I just installed today’s update (Version 7.0.2 (17812)).
The behavior is the same–the replacement banner is shown in the General tab and saved in Resources.
Checking/unchecking “use master style” in the inspector has no effect.
Contacted Rapidweaver 3 days ago–no response.
Customizing a site’s banner is one of the easiest ways to create distinctive sites. RW7 was supposed to make this easy.